Method of preparing {60 -aminobenzlpenicillin

ABSTRACT

A method for preparing Alpha -aminobenzylpenicillin consisting of acylating a derivative of 6-aminopenicillanic acid, for example from an acylal derivative having the general formula   WHERE R&#39;&#39; is an alkyl C1-C4 group, an alkyl halide, aryl or aralkyl groups with an activated ester of N-substituted D(-) Alpha -amino phenylacetic acid having the general formula   AND X is either hydrogen, or 2-pyrimidyl, in an organic solvent medium with subsequent hydrolysis.

United States Patent 1191 Rabinovich et al.

14 1 Feb. 4, 1975 22 Filed: May 18, 1972 21 Appl.NO.1254,677

[30] Foreign Application Priority Data Primary Examiner-Nicholas S. Rizzo Attorney, Agent, or Firm-Holman & Stern [57] ABSTRACT A method for preparing a-aminobenzylpenicillin consisting of acylating a derivative of 6 -aminopenicillanic acid, for example from an acylal derivative having the general formula S cw H N I clH Rm,

C0 N cH-CO0R May 18, 1971 U.S.S.R 1651444 F Apr. 24, 1972 U.S.S.R 1772937 "here [52] U.S. Cl. 260/239.1, 424/271 51] Int. Cl C07d 99/16 QR [58] Field of Search 260/2391 P HJCQ oz 3 [56] References Cited UNITED STATES PATENTS where R is an alkyl C,C group, an alkyl halide, aryl 2,985,648 5/1961 Doyle 6161. 260/2391 or aralkyl g oups with an activated ester of N- 3,282,926 11/1966 Brain c1 :11. 260/2391 Substituted D()a-amino phenylacetic acid having the 3,453,263 7/1969 Dvonch c1 a1. 260/239,] general formula Q /1400 so NHX,

NHZ

no, 0 wherezbo- 3 OCOCH c=c1-1c 3,651,050 3/1972 Nakanishi 260/2391 and X is either hydrogen, or 2-pyrimidyl, in an organic 3,697,507 10/1972 Frederiksen et a1. 260/2391 solvent medium with subsequent hydrolysis.

6 Claims, N0 Drawings METHOD OF PREPARING and where R is an alkyl group of from C C an alkyl a-AMINOBENZYLPENICILLIN halide, an aryl, or an aralkyl group, which is prepared. e.g., by the addition of an a,.,B-unsaturated ether to the The present invention relates to a method for preparcarboxyl group of an N-substituted o-aminopenicillanic ing a-aminobenzylpenicillin (ampicillin), and prepara- 5 acid (o-APA) with subsequent removal of the moiety tion has a wide antimicrobial action and is used extenprotecting the amino group. Salts of the o-APA along sively in treating diseases caused by both gram-positive with organic and mineral acids, as well as N-acyl derivand gram-negative causative agents. atives of 6-APA can be used as the N-substituted deriv- The invention comprises acylating a derivative of 6- atives of 6-APA. Thus, the acylal derivatives of 6-APA aminopenicillanic acid with activated esters of N- It can be obtained by desacylation of acylal derivatives of substituted D()a-aminophenylacetic acid having the penicillin G or V by known methods. general formula A silyl derivative of 6-aminopenicillanic acid, which Q can X is hydrogen or Z-pyrimidyl, may also be used as the starting compound in the dein an organic solvent medium and in the presence of scribed method, has the general formula O NHX (1) CH (In) co-u-' cn coast/Rh acetic acid with a subsequent hydrolysis step. The reacwhere R may be the same or different alkyl groups. and

tion solution resulting from the acylation and hydrolyis prepared by heating a reaction mixture containing sis steps gives a-aminobenzylpenicillin. Wherever nec- 6-APA and more than 2 gram-molecules of N-trialkylessary, a non-toxic salt can also be obtained therefrom. silyldialkylamine. e.g. N-trimethylsilyldiethylamine.

The activated ester of N-substituted D()awith a subsequent removal by distillation of the dialkaminophenylacetic acid having the above formula (l) 40 ylamine formed in the reaction.

is obtained by protecting the corresponding amino According to the herein proposed method. the said group in the D()a-aminophenylacetic acid by treating derivatives of the 6-APA and the acylating agent. and it with furfuryl ester of chlorocarbonic acid or with the activated ester (1), can be easily reacted in the o-nitrophenylsulphenyl chloride, or, with benzoylacepresence of acetic acid by stirring the liquid mixture of tone, with a subsequent treatment ofthe resulting prodthe starting compound and the acylating agent at room uct with N-(2-pyrimidyl)-l-phenol-4-sulphonamide or temperature for a few hours in a medium of methylene l-phenol-4-sulphonamide. chloride or chloroform or other halide-containing sol- The starting material for the proposed preparation is vents or ethylacetate.

an acylal derivative of 6-aminopenicillanic acid having This invention is characterized by the fact that the the general formula said acylation reaction employs an activated ester wherein R is selected from a group having the formula formed by treating N-substituted D()aaminophenylacetic acid (in which the amino group is protected by a special radical) with phenolsulphonamide. Owing to the use of such activated esters, the acylation reaction can be effected at a low temperature H C with a high yield of the product. 3 5 After the product of acylation has been obtained, the I protection group can be easily removed by hydrolysis,

a providing that the pH of the solution is maintained 0R below 4.0 for a short time.

1f the acylal derivative of 6-APA (I1) is used as the starting compound, the acylation process results in an acylal derivativeof N-substituted ampicillin, in which the acylal group is easily hydrolyzed under by the action of water with the formation of a free carboxyl group.

1f the trialkylsilyl ester of 6-N-trialky1- silylaminopenicillanic acid (111) is used as the starting compound, the acylation results in a silyl ester of the N-substituted ampicillin. The silyl group may also be easily removable (together with the protection group or the amino moiety) in the above reaction by hydrolysis. Moreover, the silyl group can be eliminated easier if wateror alcohol is added to the reaction mixture. Hence, it is necessary to keep the reaction mixture anhydrous at least until the completion of the 'acylation reaction.

The proposed method can be illustrated by the following examples. I

EXAMPLE 1 15.1 g of D(-)a-aminophenylacetic acid are dissolved in 100 ml of a 1N solution of NaOH, to which 100 ml of dioxane are added and the solution obtained is cooled to C. A freshly prepared solution of 16.1 g of furfuryl ester of chlorocarbonic acid in 500 ml of sulphuric ether are then added gradually with stirring with a current of nitrogen. 25 ml of 4N solution of NaOH are simultaneously added to the mixture to maintain the pH of the medium at 8.5-9.0. The mixture is continuously stirred with cooling for l hour. As soon as the reaction is completed, the aqueous-alkaline solution is separated, and washed with ether and acidified with 2N sulphuric acid to a pH of 3.0-3.5 at 0C. The precipitated N-carbofurfuryloxy-D()a-aminophenylacetic acid is washed with water till the acid reaction vanishes, then dried at room temperature.

3 g of the thus obtained product, N-carbofurfuryloxy- D()a-a-minophenylacetic acid are dissolved in 20 ml of anhydrous pyridine whereupon 2.5 g of N-(2- pyrimidyl)-l-phenol-4-sulphonamide are added. The solution is then cooled to 0C, and 1.58 g of phosphorus oxychloride in 5 ml of methylene chloride are slowly added within 30 minutes. The reaction mixture is stirred at room temperature, and 300 ml of ice-cold water are added. The precipitated N-(2-pyrimidyl)-4- sulphonamide-l-phenyl ester of N-carbofurfuryloxy- D(-)a-aminophenylacetic acid (I) is washed several times until the odour of pyridine is absent, and then dissolved in 20 ml of methylene chloride. Magnesium sulphate is added to the solution and the contents are agitated. The solution is dehydrated and filtered.

The acylal derivative of 6-APA is prepared simultaneously, for which purpose 3 g of 6APA are suspended in 4.5 ml of formic acid at a temperature of 0-5C. 7.5 g of A -dihydropyran are then added to the prepared suspension and the mixture is stirred for 10-15 minutes until a homogeneous solution is obtained. The formed acylal formylate and excess A -dihydropyran are distilled in a vacuum to give 4.3 g of an acylal of 6-APA (Z-tetrahydropyranyl ester of 6-APA). The filtrate is mixed with a solution of 3.5 g of an acylal of 6-APA in methylene chloride and with the obtained ester having formula (I), and then 0.5 ml of acetic acid is added and the components are mixed fora few hours at room temperature. As the acylation reaction is completed, the methylene chloride is removed by distillation and the residue is treated with a solution of 1.6 g of hydrogen bromide in 20 ml of acetic acid at 0C for 3 minutes. Upon completion of the hydrolysis, the solution is diluted with 2 volumes of water and washed with butyl acetate. The pH of the aqueous solution is adjusted to 5.0-5.5 by adding 10 per cent of an alkali solution and the desired product, a-aminobenzylpenicillin trihydrate, is isolated. The yield of the product is 3.2 g which is 76.1 per cent oftheory. The purity ofthe product is 96 per cent.

EXAMPLE 2 in vacuum. The resultant product is 5.0 g of ampicillin trihydrate. The purity of the product is 35 per cent.

EXAMPLE 3 3.0 g of N-[ l-methyl-2-benzoylvinyl]-D(-)aaminophenylacetic acid are converted to M2- pyrimidyl)-l-phenol-4-sulphonamide ester and condensed with 3.5 g of acylal of 6-APA obtained by reacting 6-APA with 2-methyl-N-dihydrofuran under the conditions described in Example 1. N-substituted ampicillin is hydrolyzed under the conditions described in Example 2. The resultant product is 4.0 g of ampicillin trihydrate. The purity of the product is 30 per cent.

EXAMPLE 4 3.0 g of N-carbofurfuryloxy-D()aaminophenylacetic acid are converted to N-[2- pyrimidyl]-l-phenol-4-sulphonamide ester and reacted with 3.6 g of a trimethylsilyl ester of -N-trimethylsilylaminopenicillanic acid in methylene chloride. whereupon 0.5 ml of acetic acid is added and the components are stirred for a few hours at room temperature. Upon termination of the reaction of acylation, the methylene chloride is removed by distillation. and the residue is treated as described in Example 1. The yield of the desired product is 3.25 g, which is 77.4 per cent of theory. The purity of the product is 96 per cent.

EXAMPLE 5 3.0 g of N-lo-nitrophenylsulphenyl]D()aaminophenyl acetic acid are converted to N-[Z- pyrimidyl1-1-phenol-4-sulphonamide ester and reacted with 3.6 g of a silyl derivative of 6-aminopenicillanic acid (111) under the conditions described in Example 4. After the methylene chloride has been distilled off, the remaining N-substituted ampicillin is dissolved in acetone, diluted with an equal volume of water, acidified with hydrochloric acid in order to adjust the pH of the medium to 2.0, stirred for 2 hours at O-lC whereupon the acetone is distilled off. The remaining aqueous solution is washed with butyl acetate, and the pH of the aqueous layer adjusted to 5.0-5.5 by adding alkali, and the aqueous layer evaporated in vacuum. The resulting product is 4.6 g of ampicillin trihydrate. The purity thereof is 35 per cent.

EXAMPLE 6 formula: I

so uax j \CHOO NHZ where Z is selected from the group consisting of:

X is selected from the group consisting of hydrogen and Z-pyrimidyl, at room temperature in a reaction-inert organic solvent medium in the presence of acetic acid, and hydrolyzing the reaction product to remove the protecting groups.

2. A method as claimed in claim 1, in which the acylal derivative of the 6-aminopenicillanic acid has the formula S CU 3' HZN CH CH C l ca CO N CH COOR where R is a moiety selected from the group consisting of where R is selected from the group consisting of an alkyl of from C -C B-chloroethyl, phenyl and benzyl.

3. A method as claimed in claim 2, in which an acylal derivative of 6-aminopenicillanic acid obtained by reacting an a,B-unsaturated ether selected from the group consisting of CH CH *OR, where R is selected from the group consisting of an alkyl of from C C B-chloroethyl, phenyl and benzyl, is used to form the N-substituted-- aminopenicillanic acid.

4. A method as claimed in claim 1, in which a trialkylsilyl derivative having the general formula where R is alkyl, is used to form the derivative of 6- aminopenicillanic acid.

5. A method as claimed in claim I. in which methylene chloride is used as the organic solvent.

6. An acylal derivative of -aminopenicillanic acid wherein the acylal moiety has the formula 5 ca 3 H NCHCh c I I CH3 CO-N h ca cooa where R is selected from the group consisting of Q 3i CH CH3 where R is selected from the group consisting of an alkyl of from C -C B-chloroethyl, phenyl and benzyl. =i l 

1. A METHOD FOR PREPARING A-AMINOBENZYLPENICILLIN COMPRISING REACTING AN ACYLAL DERIVATIVE OF 6-AMINOPENICILLINANIC ACID WITH AN ACTIVATED ESTER OF N-PROTECTED D(-)AAMINOPHENYLACETIC ACID HAVING THE FORMULA:
 2. A method as claimed in claim 1, in which the acylal derivative of the 6-aminopenicillanic acid has the formula
 3. A method as claimed in claim 2, in which an acylal derivative of 6-aminopenicillanic acid obtained by reacting an Alpha , Beta -unsaturated ether selected from the group consisting of
 4. A method as claimed in claim 1, in which a trialkylsilyl derivative having the general formula
 5. A method as claimed in claim 1, in which methylene chloride is used as the organic solvent.
 6. An acylal derivative of 6-aminopenicillanic acid wherein the acylal moiety has the formula 